Mechanism for adjusting the resistance



July 3. 1956 E. .C. WALKER, JR

2,753,117 MECHANISM FOR ADJUSTING THE RESISTANCE TO KEY DEPRESSIONS IN CALCULATING MACHINES Filed Sept. 22, 1954 2 Sheets-Sheet l INVENTOR.

Emil C Wad/(623% I 6 loczzau July 3. 1956 c. WALKER. JR 2,75

E MECHAN FOR ADJUSTING THE RESI NCE TO SIONS IN CALCULATING KEY D ES A HINES Filed Sept. 22, 1954 2 Sheets-Sheet 2 INVENTOR.

fmil C, Walker; Jr.

20 M,Q@Q@Z a United States Patent MECHANISM FUR ADJUSTING THE RESISTANCE TO KEY DEPRESSIGNS IN CALCULATING MACHINES Emil C. Walker, .ln, Woodstock, Ill, assignor to Felt and Tarrant Manufacturing Company, Chicago, 111., a corporation of Illinois Application September 22, 1954, Serial No. 457,659

Claims. (Cl. 235-145) This invention relates in general to calculating machines, and more particularly to mold-denominational order machines having a plurality of digit control keys in each denominational order.

A principal object of the invention is to enable any machine operator readily to selectively adjust such a machine to his or her individual touch or style of digit key depression.

Another important object of the invention is to provide touch control mechanism, in such a machine having a spring in each order tensioned by depression of any denominationally associated digit key, whereby simple selective movement of a single control member is all that is required to simultaneously vary the initial tension uniformly in all of those springs so as to adjust the entire keyboard to best accommodate the individual touch of any operator.

A further important object is to provide such touch control mechanism, in a machine with a readily separable keyboard unit, which comprises movable mounting means for the tension-adjustable springs having stop means for limiting movement thereof, together with selectively adjustable control means mounted on the keyboard unit so as to be freely removable therewith and automatically disconnectable from and connectable with the spring mounting means, whereby removal of the keyboard unit will entail no additional or special consideration being given the touch control mechanism.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, when taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

In the drawings:

Figure 1 is a longitudinal, vertical section taken through a calculating machine, in which a preferred embodiment of the invention has been incorporated, on a plane to the left of the highest denominational order and as viewed from the left side of the machine, with certain of the conventional parts omitted for purposes of clarity;

Fig. 2 is a top plan View of the forward portion of the calculating machine of Fig. 1;

Fig. 3 is a detail vertical section taken substantially on the line 33 of Fig. 1;

Fig. 4 is a detail horizontal section taken substantially on the line 4-4 of Fig. 3; and

Pig. 5 is a perspective view of the selectively adjustable means forming part of the present touch control mechanism as it appears when separated from the keyboard unit.

Referring more particularly to the drawings, the present invention is illustrated for convenience as being incorporated in a power driven, key-responsive calculating machine of the type known commercially as the Comptometer calculating machine and more specifically described in United States Letters Patent No. 2,063,962, issued December 15, 1936, although it will be understood from the following detailed description that it is susceptible Patented July 3, lie 5 5 vi of use in numerous other types of mold-denominational order calculating machines.

As illustrated more in detail in Patent No. 2,063,962, the calculating machine herein shown as embodying the present invention is housed in a suitable outer casing 21 (Fig. 2) having an opening in its upper surface closed by a top plate 22 of a ke carrying frame or keyboard unit bodily removable, as is the casing, from skeleton frame plates 23 (Fig. 1). The actuating and control mechanisms of the several denominational orders are disposed between and carried by the frame plates 23, which are secured together in spaced relationship at suitable points by tie rods 24. A plurality of digit keys 25 in each denominational order forming part of the control mechanism have stems 26 vertically slidably arranged in the keyboard unit in the usual manner for determining the digital degree of the calculating movements in the associated order. Upon depression of any digit key 25 and its key stem 26, power is supplied from a power shaft 27 to extend an actuator spring 28 associated with the particular denominational order of mechanism with which the depressed key is identified, release of this spring thereafter accomplishing adding movement in an amount determined by the particular key depressed through the agency of a gear sector or segment 29. Each gear sector 29 meshes with a transmitting pinion or accumulator actuating gear 31 rotatably mounted on a stationary transverse shaft 36 which is journaled in the several skeleton frame plates 2-3. Each denominational order of the accumulator also includes a gear train (not shown) for transmitting actuation of the pinion 31 to an associated numeral wheel gear 36. Secured to each numeral wheel gear 36 and rotatably mounted on a stationary transverse shaft 37 is a numeral wheel Well-known carrylug mechanism is provided in each denominational order of the accumulator for the purpose of imparting a digital unit of actuation thereto each time that a l0s transfer is to take place from the next lower denominational order or the accumulator.

Depression of any one of the digit keys 25 causes its stem 26 to engage an upper bar of a parallel motion device, also forming part of the control mechanism, which is pivoted at the front of the machine at 42 (at the right in Fig. l) and at the rear at 43 to levers 44 and 45, respectively, which levers are pivoted in turn upon cross shafts or rods 4-6 extending through the partition plates 23. A lower link 47 is pivotally connected at 48 to the lever 44 and at 49 to the lever 45. The bar 41, levers 44 and 4-5 and the link 4'7 form part of this parallel motion device, and are constructed and mounted as shown and described in detail in Patent No. 2,063,962. Each of the gear or rack sectors 2? is articulately connected to a hook by a link 52 through a yielding clutch 53, the hook 5i and link 52 being articulately connected to a substantially vertical guide member 54, which is pivotally mounted at its lower end on a suitable transverse shaft. Each gear sector 29 also is articulately connected to a movement controlling or stop bar 55 by a link 56. A spring 57, which is attached to the rear lever 45 and to a latch member 58 carried by the bar 4-7, normally contributes towards holding the parallel motion device in its elevated position of Pig. 1, and also holds the lower end of latch member 58 in a forward position (to the right in that figure) for a purpose presently LU be explained. A dog 59, which is pivoted at its upper end on the parallel motion bar ll, is provided with a laterally extending lug on its lower end for engagement with a horizontal shelf on a spring-lifted lever 61 pivotally mounted on the guide member 54 with the hook 51.

The operation or" these parts in each denominational order is such that, upon depression of a digit key 25', its stem 26 engages and depresses the bar 4-1 to impart motion to the parallel motion device, which carries dog 59 downwardly to depress the lever 61. The spring mounted on the pivot between the link 52 and the hook 51 engages the lever 61 and the hook to urge the rear end of the latter (left end in Fig. 1) downwardly, so that it will normally cause engagement of the hook 51 with a toothed wheel 62 upon depression of lever 6 The toothed Wheel 62 is secured to the power shaft 27, which turns in a counter-clockwise direction viewing Fig. l. The engagement of the hook 51 with the wheel 62 pulls the link 52 toward the rear of the machine, or to the left viewing Fig. 1, which imparts downward motion to gear sector 29 through the yielding clutch 53. Forward motion is thus imparted to the digital control or stop bar 55 until one of the several lugs projecting laterally therefrom is stopped by the stem 26 of the depressed digit key. The rearward motion of hook 611 and link 52 causes the guide arm 54- to swing in a counter-clockwise direction from its normal position of Fig. 1 to extend the spring 28, one end of which is connected to this guide arm and the other end to a transverse shaft extending through the skeleton frame plates. The link 52 moves the rack or gear sector 29 downwardly on an idle stroke in response to such swinging of the guide arm 54 and into position to impart an adding movement of the accumulator upon release of the hook 51 and contraction of the spring 25. The downward movement of gear sector 29 is under the control of the digital stop bar 55 and the gear sector is halted when it has been moved downwardly the proper distance, enabling it upon return to impart the degree of digital advancement to the adding mechanism which corresponds to the particular key 25 depressed. The yielding clutch 53 permits the continuation of the rearward movement of link 52, after downward movement of the gear sector has been stopped, and until the end of the full power stroke and the automatic release of the hook 51 from the toothed wheel 62. Release of hook 51 is accomplished automatically in each instance, after a set increment of action has been imparted to the link 52, by the teeth of the wheel 6'2. Upon the return or upward stroke of the gear sector 29, the yielding clutch 53 permits relative movement of the parts in reverse direction to that at the beginning of the adding movement, and thereafter this adding actuation is accomplished.

The latch member 53 is provided to prevent return movement of the dog 59 before the hook 51 has been engaged with the toothed Wheel 62 in response to depression of a digit key 25 and to insure retention of the depressed key, when it has been fully depressed, until it has served its movement limiting function in conjunction with the stop bar 55. This latch member 59 is pivotally mounted at its upper end on the link .7, and the rear portion of its lower end is adapted to engage upon a lateral projection of the dog 59 to hold the dog down against upward return movement and also to hold the parallel motion device in depressed position. As is described in detail in Patent No. 2,063,962, engagement of the hook 51 with the toothed wheel 62 does not take place until a digit key 25 has been completely depressed. Following complete depression of a digit key 25 and engagement of the hook 51 with toothed wheel 62, the latch member 58 is swung in a clockwise direction (viewing Fig. 1) to release the dog 59 just prior to the automatic release of hook 51 from its toothed wheel 62. This release of dog 5% is accomplished by a pin 63 provided in an upwardly extending arm of the vertical guide member 54, which, through its connection with the hook 511, has been carried rearwardly, the pin 63 engaging a finger 6d of latch member 58 to swing the latter in a clockwise direction to free the dog 59 so that the parallel motion device may be spring returned to normal raised position.

As previously noted, the spring 57 assists .in such return of the parallel motion device to its normal position of Fig. l, which is accomplished in response to the abovedescribed power release oflatch member 58 from-engage! ment with dog 59. In prior machines of this specific type, an additional spring has been provided in each denominational order for assisting in such return movement of the parallel motion device. In Fig. 5 of U. S. Patent No. 2,241,102, issued May 6, 1941, such a spring is designated by reference numeral 161 and is shown interconnected between a depending lug on the top key bar 138, which is similar to key bar 41 herein, and the front lever 142, herein identified by numeral 44.. The same spring is illustrated just above the reference numeral 46 in Fig. l of U. 5. Patent No. 2,224,203, issued December 10, 1940. The reaction of this spring (not shown herein but designated in Patent No. 2,241,102 by numeral 161) is the greatest of the several forces tending to return the parallel motion device to normal position, and hence represents an appreciable part of the resistance to be overcome by a machine operator in depressing a digit key 25. In accomplishing the objects of the present invention, this particular spring has been eliminated from each denominational order and a different spring (herein designated by reference numeral 201) so substituted therefor as to enable selective variation of its normal tension or reaction, in a manner to be later described, so as to adjust the resistance to key depression to meet the requirements or individual touch of different operators.

For a full and complete appreciation that such substituted springs and the additional mechanism enabling their use, which will be described in detail hereinafter, have not impaired or altered any of the usual functions of the parallel motion devices, it is thought best to briefly describe two more functions of the latter in addition to those so far enumerated. Error control mechanism is provided for insuring proper operation of the accumulator in the manner above described by requiring a full stroke to be given any digit key 25 depressed, and locking up the keyboard in the event of mismanipulation or partial depression and release of any digit key and until corrective complete depression of the mismanipulated key or keys. Such error control mechanism is completely illustrated and described in U. S. Letters Patent No. 2,018,933, dated October 29, 1935, and lo. 2,224,203, issued December 10, 1940. Only those parts thereof are shown in Fig. 1 herein suficient to an understanding of their operation in connection with the present invention. In each denominational order of the machine, the parallel motion device includes a key-locking bar 101 having rearwardly extending locking lugs or teeth 102 normally disposed, respectively, in front of each of the stems 26 of the digit keys 25 of that order. The bar 101 is pivoted upon studs 103 extending through slots 104 in the associated upper bar 41 of the parallel motion device and connected to the upper ends of the levers 44- and 45. B y virtue of such mounting of the bar 1621, as any digit key 25 is depressed from its normal position of Fig. 1, the lower end of its stem 26 passes its associated tooth 102 and impinges against the top of the bar 41. to lower the latter and .move the bar 101 rearwardly (to the left in Fig. 1). In this rearward movement of the bar 101, the end of the tooth 102 associated with the depressed key enters an aperture (not shown) in the key stem 26. Continued depression of the digit key 25 in lowering bar 41 and moving bar 101 rearwardly also moves the lower link 47 of the parallel motion device forwardly, and the resulting downward movement of dog 59 and forward movement of latch member 5%; permits swinging of the latter by its sprin 5'7 to prevent return movement of the parallel motion device following complete depression of the digit key until the power release of latch 58 as above described.

In the event of partial depression and release of a digit key 25, the error control mechanism prevents complete return of the parallel motion device to normal position in the following manner. That error control mechanism includes in each denominational order of the machine a latch or dog 105 pivoted on the denominationally associated link 47, and a spring normally presses a lip on the rear end of the dog 105 upwardly into contact with the lower edge of the link 47. A ratchet tooth is provided upon the upper portion of a lever 108 pivoted at its lower end in a bracket 111 which, in turn, is pivoted on a cross rod 112 extending through the skeleton frame plates 23 of the machine. A spring 113 is attached to the lower end of the lever 19S and to a lever 114 which is pivoted at its lower end upon a cross rod 115. Upon depression of any one of the digit keys 25 in that denominational order, the link 47 forming part of the parallel motion device is moved toward the right, as seen in Fig. 1, and the latch or dog 105 being carried by it moves with it and past the ratchet tooth on lever 108. If the digit key is released prior to fully effective depression, such forward movement of link 47 will be incomplete, and springs 57 and 201 function to return the parts toward their original position of Fig. 1 without accomplishing any calculating operation. A link 117 is pivoted at its forward end to the upper end of the lever S, and at its rear end to a downwardly extending pivotally mounted arm 119. it mismanipulation of the digit key occurs, comprising insufficient down stroke and release thereof, the resulting rearward return movement of link 47 causes dog 165 to engage the ratchet tooth on lever 1G8 and move link 117 rearwardly to set up the interordinal keyboard looks, as described in Patent Nos. 2,018,933 and 2,224,203, and to prevent complete return of the parallel motion device. In thus being stopped short of complete return to the normal position of Fig. l, the tooth 1492 of the locking bar 101 associated with the mismanipulated digit key 25 remains in the aperture in the stern to prevent complete return of the released digit key by the usual spring (not illustrated) connected thereto. The mismanipulated digit key 25 is thus locked in a partially depressed indicating position, without having caused operation of the accumulator actuating mechanism, but may be correctively actuated to effect proper operation of the accumulator by being completely depressed. Means are provided for moving the ratchet tooth on the lever 108 outof the path of the dog 1'85 if and when such full key-stroke is accomplished. Each bracket 111 is provided with a downwardly extending arm 1.24 which is disposed across the path of movement of a lateral lug 125 upon the associated link 52. As the parts near the end of he power stroke resulting from complete depression of a digit key 25, the lug 25 engages the arm 124 and lifts the bracket 111 about its pivot 112, carrying up the lever 103 to raise the ratchet tooth thereon above the lower edge of link 47 and out of the way of the dog 105. The lever 1&8 has a portion res which is adapted to engage above a shoulder 127' on the lever 114 when the lever 108 is thus lifted by lug 1255. The lever 198 is held in such upper latched position until near the end of the return or power stroke, when a lug 128 on the link 47 engages the upper end of lever 114 to disconnect it from the shoulder Lift-5, thereby arranging the parts in the normal position of Fig. 1 for the next calculating operation.

To the above described and other well-known mechanisms comprising a complete operative calculating machine, the present invention has added means selectively adjustable to vary the resistance normally offered to depressions of tie digit keys 25, so that a simple movement of a single control member is all that is required to set the machine to best accommodate the individualistic touch of any operator. As previously noted, this means comprises a spring substituted in each denominational order of the machine the spring heretofore interconnecting the upper key bar 41 and the front lever 44 of the parallel motion device. As previously noted, such springs are designated herein by reference numeral 2%1. As best seen in Fig. 1, each spring 201 is connected at its rear end to a link 292 having a bayonet slot engaging the shank of a headed stud 263 mounted on the associated key locking bar 101. The forward end of each spring 201 is connected to the lower end of a lever 204 which is mounted upon and rigidly secured to its upper end in any suitable manner to a transverse shaft 205 extending across the front part of the machine and journaled in the frame plates 23. Referring to Figs. 1, 3, and 4, the left end of the transverse shaft 2G5 has secured thereto in any suitable manner adjacent the leftmost frame plate 23 a cam plate 206 carrying a cam roller 207 and also being formed to provide stop means in the of shoulder 208 (Fig. 1). This stop shoulder 32% cooperates with the usual spacer collar on the adjacent transverse tie-rod 24 to limit clockwise movement of shaft 205, as seen in Fig. 1, under the influence of the several springs 201. A minimum degree of initial tension is thus maintained in the springs 201 when the several levers 294 are disposed in their rearmost position, as shown in full lines in Fig. 1, as limited by the stop shoulder 203 of plate 206 contacting against the adjacent tie-rod 24 or the spacer collar surrounding the same. The above-described members 204-2il8 thus comprise mounting means for the several springs 201 for maintaining an initial tension therein which, in the case of each spring 2&1, contributes an appreciable part of the resistance to be overcome by an operator in depressing any one of its several denominatio-nally associated digit keys 25.

For cooperation with the cam roller 2G7, a cam slide 299 is provided having an inclined cam surface 211 (Fig. 5) at its forward end which engages the roller 297. As best seen in Figs. 1 and 5, the cam slide 2% is mounted for limited movement in a substantially U-shaped guide bracket 212 having horizontally disposed flanges 213 at its upper end which are secured in any suitable manner (Figs. 1, 3, and 4) to the top plate 22 of the keyboard unit. As best seen in Figs. 1 and 4, this top keyplate 22 is provided with a suitable slot 21a to accommodate an upwardly extending stem portion 215 of the cam slide 2tl9. This stem portion 215 is suitably formed at its upward end (Fig. 5) to detachably receive a finger piece 216, best seen in Figs. 1 and 2. interposed between the bottom portion of the guide bracket 212 and the lower horizontal edge of the cam slide 2&9 is a wire leaf-type or camber spring 217. in order to prevent displacement of this spring 217 longitudinally of the cam slide 209 and bracket 212, it is preferred that the rear end thereof be bent downwardly, as shown in Fig. 5, through a suitable aperture in the bottom wall or" the guide bracket 212. One or both of the vertical side walls of the bracket 212 are provided with suitable apertures through which the inturned ends of a keeper 218 are disposed for cooperation with the upper edge of the cam slide 2 39. As best seen in Figs. 1 and 5, the forward portion of the upper edge of the cam slide 209 is serrated or provided with a plurality of cam teeth 219 which cooperate with the forward inturned end or" the keeper 218 and the camber spring 217 permit longitudinal adjustment of the cam slide 289 and to automatically retain that slide in any of its several possible adjusted positions. The rearmost longitudinally adjusted position of the cam slide 209 is that illustrated in full lines in Fig. 1, wherein the cam surface 211 thereon is still in contact with the cam roller 2 57, although the stop shoulder 298 of the plate 206 mounting the roller is in contact with the adjacent tie-rod 2d, and it is preferred that some means be provided to limit rearward movement of the slide 209 to that extent. As illustrated in Figs. 1 and 4, the slot 214 in the top keyplate 22 is of such length as to engage the stem portion 215 of the cam slide 269 to comprise such a rearward movement-limiting means for the slide, although the rear inturned end of the keeper 218 may be so positioned as to similarly cooperate with the stem portion 215 if desired. As shown in broken lines in Fig. 1, forward longitudinal adjusting movement of the cam slide 2%? is limited by engagement of its forward upper end with the tie-rod 24 or its spacer sleeve with which the stop shoulder 298 cooperates. As will readily be appreciated, movement of the cam slide 209 between these two extreme rearward and forward positions, through the agency of the finger piece 216, will result in all of the levers 204 being moved between their two extreme positions as illustrated in full and broken lines, respectively, in Fig. 1.

Such longitudinal sliding adjustment of the slide 209 is against the action of the camber spring 217, the teeth or serrations 219 constituting cam means on the slide which cooperate with the forward inturned end of the keeper 218 to depress the forward portion of the cam slide 209 sufiiciently to permit longitudinal movement of the latter. The several parts 209-219 thus comprise selectively adjustable control means for moving the mounting means for all of the springs 2&1 simultaneously to uniformly vary the initial tension of each of those springs to adjust the entire machine to suit the individual style of digit key depression of any operator. The keeper 218 not only limits movement of the cam slide 209 and cooperates with the teeth 219 and camber spring or spring device 217 to maintain slide 209 in any longitudinally adjusted position, but also cooperates with the teeth or cam means 219 to translate longitudinal movement of slide N9 into vertical movement thereof against the action of spring device 217 to permit the desired adjustments of the cam slide and the mounting means for springs 291. The full line positions of the several parts illustrated in Fig. 1 result in the minimum possible initial tensioning of the several springs 201. Forward adjustment of the slide 269, using the finger piece 216, will result in the cam edge 211 of the slide cooperating with the cam roller 2&7 to rotate the plate 206, shaft 205, and all of the depending levers 204 in a counterclockwise direction, viewing Fig. 1, to uniformly increase the normal or initial tensioning of all of the several springs 201. The levers 2%, comprising the mounting means for the several springs 2M, are selectively adjustable simultaneously, through the agency of the finger piece 216 and interconnected parts, to uniformly vary the initial tension of each of the springs 2M to adjust the machine to suit the individual style of digit key depression of any operator. With the adjustable features above described it is thus assured that any adjustment of the finger piece 216 that is made Will cause identical alteration to the resistance offered to each and every one of the digit keys 25 in each and all denominational orders of the machine.

Another distinct advantage of that modification of the invention herein illustrated is that the keyboard may be removed as a unit from the frame plates 23, just as before the introduction of the touch control mechanism added by this invention, without requiring any special consideration being given to the instant touch control mechanism during such removal of the keyboard unit. With particular reference to Fig. 1, it will be seen that the stop means or shoulder 293 comprising part of the mounting means for the springs 291 limits movement of such mounting means by those springs upon removal of the keyboard unit with the selectively adjustable control means 209-219 from the frame plates 23, so as to prevent damage to the mounting means or misalignment thereof While the keyboard unit is removed. Such arrangement also maintains the mounting means in position for proper operative engagement by the cam slide 239 of the selectively adjustable control means with the cam roller 207 when the keyboard unit is replaced on the frame plates 23, the cam roller 26''] and slide 2h9 providing a readily separable and re-engageable connection between the spring mounting means and its selectively adjustable control means. From Figs. 1, 2 and 4 it will be seen that the finger piece 216 also functions as a dust guard, since it covers the longitudinal aperture 214 in the top key plate 22 in all adjusted positions of the slide 299. And it will be appreciated from the preceding description, that the structure comprising the illustrated embodiment of the present invention is simple to manufacture and assemble, and is specifically adapted to be readily incorporated into the existing commercial embodiments of the machines illustrated in the several patents hereinbefore identified.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing rom the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

I claim:

1. A calculating machine, comprising a multi-denominational order accumulator; actuating mechanism for said accumulator; control mechanism for determining the digital degree of operation of said accumulator by said actuating mechanism, including control devices in each denominational order, a plurality of digit keys for actuating each of said control devices, and a spring connected to each of said control devices for assisting in returning the same to normal position following depression and release of any denominationally associated digit key; and selectively adjustable means for varying the initial tension of said springs to accommodate the individual touch of any operator, including a single finger piece movable to eifect the same variations in initial tension in all of said springs, a cam slide movable by said finger piece, and means for automatically releasably retaining said cam slidein any one of a plurality of selectively adjustable positions.

2. In a calculating machine having a multi-denominational order accumulator, actuating mechanism therefor, and a plurality of denominational orders of control mechanism movable from normal position to control operation of said accumulator by said actuating mechanism, including in each order a plurality of depressible digit keys respectively determining the digital degree of operation of said accumulator by said actuating mechanism; spring means in each order tensioned by the depression of any one of the denominationally associated digit keys to assist in returning said control mechanism in that order to normal position, mounting means for each of said spring means maintaining an initial tension thereon, and selectively adjustable means for moving all of said mounting means simultaneously to uniformly vary the initial tension of each of said spring means to adjust the entire machine to suit the individual style of digit key depression of any operator, said selectively adjustable means including a cam slide movable longitudinally to any one of a plurality of selected positions to effect corresponding movement of said mounting means.

3. In a calculating machine having an accumulator, actuating mechanism for said accumulator, control mechanisms for said actuating mechanism including springs assisting in maintaining the same in normal inactive position, stationary frame plates for supporting said accumulator, actuating and control mechanisms, and a keyboard unit removably mounted on said frame plates and including digit keys depressible to selectively operate said control mechanisms against the action of said springs; touch control mechanism for varying the initial tension in said springs to change the resistance to depression of said digit keys to suit the individual touch of different operators, comprising mounting means attached to said springs and carried by said frame plates, and selectively adjustable control means mounted on said keyboard unit for moving said mounting means to determine the initial tension in said springs and freely removable with said keyboard unit from operative engagement with said mounting means, said mounting means comprising stop means to limit movement thereof under the influence of said springs which prevents damage thereto and misalignment of the mounting means, upon removal of said keyboard unit, and maintains said mounting means in position for proper operative engagement by said selectively adjustable control means when said keyboard unit is replaced on said frame plates, and a cam roller mounted on said plate, and said selectively adjustable control means comprising a cam slide normally engaging said cam roller, said cam slide and roller providing a readily separable and re-engageable connection between said mounting means and said selectively adjustable control means.

4. A calculating machine according to claim 2, wherein said selectively adjustable means includes a keeper for limiting movement of said cam slide, a spring device urging said cam slide into engagement With said keeper, and cam means formed on said cam slide for cooperation with said keeper to translate longitudinal movement of slide into limited vertical movement thereof against tl. action of said spring device.

5. A calculating machine according to claim 4, wherein said digit iceys comprise part of a keyboard unit including a top key plate having guide apertures therefor and a longitudinal aperture adjacent thereto, said cam slide being provided with a stern portion extending upwardly through said longitudinal aperture, and a finger piece detachably mounted on said stem portion to actuate said cam slide and cover said longitudinal aperture in all adjusted positions of said slide.

References Cited in the file of this patent UNITED STATES PATENTS 2,241,102 Qurck May 6, 1941 FOREIGN PATENTS 540,316 Great Britain Oct. 13, 1941 549,960 Great Britain Dec. 16, 1942 

